Sunday's accusation was the latest in a string of Turkish comments drawing Nazi parallels with present-day Germany and the Netherlands

in a dispute over restrictions on Turkish officials campaigning there in a referendum campaign.

Peter Tauber, the general secretary of Merkel's conservative party, told N24 television that "this is real effrontery toward our chancellor." However, he added that "we can allow ourselves to be outraged, stamp our feet and perhaps fight back—but the chancellor has to safeguard our country's interests."

Merkel has made clear that she doesn't intend to respond to swipes from Turkey, and the government's response was guarded. Last week her spokesman, Steffen Seibert, said she "has no intention of participating in the race of provocations."

"The German government is watching this very attentively," Ulrike Demmer, another spokeswoman for the chancellor, said when asked about Erdogan's latest comments. "It remains the case that Nazi comparisons are unacceptable, no matter in what form."